The present invention relates generally to vehicle supplemental inflatable restraint systems and, more particularly, to an air bag module that provides variable output inflation of an air bag cushion from a single inflator.
Driver side or passenger side supplemental inflatable restraint (SIR) systems typically include an air bag stored in a housing module within the interior of the vehicle in close proximity to either the driver or one or more passengers. SIR systems are designed to actuate upon sudden deceleration so as to rapidly deploy an air bag to restrain the movement of the driver or passengers. During deployment, gas is emitted rapidly from an inflator into the air bag to expand it to a fully inflated state.
Air bag passive restraint systems include an inflator, which produces gas to inflate the air bag cushion. Known inflators for air bag modules are generally of three types. One type is the pure gas inflator wherein a pressure vessel contains stored pressurized gas. The pressure vessel communicates with the cushion through various types of rupturable outlets or diaphragms. Another type is the gas generator wherein a propellant is ignited and the resultant gas created flows through an outlet to the cushion. A third type is the hybrid or augmented type. This type includes a pressure vessel containing stored pressurized gas and a gas generator. When the generator is ignited, the resultant gas flows with and heats the stored gas going to the cushion through the pressure vessel outlet.
It is also known to inflate the cushion at a relatively low rate under low level deployment conditions, such as a sudden low level deceleration, and at a relatively high rate under high level deployment conditions, such as a sudden high level deceleration. Devices are known which provide primary inflation (reduced inflation) and full level inflation using a single gas vessel with two separate gas heaters. Primary inflation is accomplished by actuating the gas vessel and heating the gas at a specified reduced level. Full level inflation is accomplished by actuating a second separate heater located at the bottom of the gas vessel to heat the gas at a greater level. This second heater is deployed at the same time or a delayed time as the primary heater to provide fall level inflation. It is also known in the art to use a system having two discrete inflators to accomplish dual level inflation. In these types of systems, two discrete inflators are deployed at the same time or at a delayed time depending upon the severity of the sudden deceleration.
This invention offers advantages and alternatives over the prior art by providing an air bag module which offers variable deployment performance by controlling the quantity and fluid flow path of the inflator gas into or out of the air bag module. The air bag module includes an inflator for generating inflator gas for inflation of an air bag cushion. The air bag module includes a cushion retainer (diffuser) having a vent opening and an annular cavity which is disposed about the inflator. The cushion retainer includes a plurality of diffuser openings which permits fluid communication between the annular cavity and the air bag cushion. The air bag module further includes an annular base plate, a pad retainer, and an adapter plate disposed about the inflator. The annular base plate, pad retainer, and adapter plate include openings which define a vent opening to provide a fluid path for the inflator gas to flow from the annular cavity to outside of the air bag module. For full level deployment, the vent opening is closed and therefore the inflator gas is not permitted to flow away from the air bag module but instead flows into the air bag cushion. The degree of reduced level deployment of the air bag cushion is dependent upon the volume of the gas directed away from the air bag cushion. In accordance with the present invention, the volume of inflator gas which flows into the air bag cushion is controlled by selecting the ratio between the cross-sectional area of the diffuser openings and the cross-sectional area of the vent opening. For example, for a low reduced level deployment, the cross-sectional area of the vent opening is increased in relation to the cross-sectional area of the diffuser openings. This may be achieved in a variety of ways, including reducing the cross-sectional area of the diffuser openings or by reducing the number of diffuser openings or by increasing the relative vent of cross-sectional area. Conversely, for increased low level deployment, the cross-sectional area of the vent opening is decreased in relation to the cross-sectional area of the diffuser openings and/or the number or size of the diffuser openings are increased so that a greater volume of inflator gas is directed toward the air bag cushion. Accordingly, the selective control of the ratio acts as a tuning mechanism by which different low level inflator outputs can be achieved.
The air bag module also includes an actuator assembly including a movable member which is movable relative to the vent opening for restricting fluid flow through the vent opening under predetermined deployment conditions. The actuator assembly has an actuator for moving the movable member and in an exemplary embodiment the actuator comprises a pyrotechnic device. In the illustrated and exemplary embodiment, the movable member comprises a slide mechanism or a stopper mechanism which closes the vent opening under predetermined deployment conditions and prevents the inflator gas from flowing away from the air bag cushion. Furthermore, controlling the timing of the vent closure provides a way to obtain variable inflation between the low and high level performance.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.